Segment Operating Results - (Footnotes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Other Revenue, net	$ 9,477	$ 1,171	$ 17,720	$ 1,351
Special Charges	1,029	0	2,058	1,897
Acquisition and Transition Costs	0	0	108	21
Total Other Expenses	6,909	5,880	14,275	13,938
Investment Banking [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	7,236	539	13,723	(889)
Interest expense on Notes Payable, Subordinated Borrowing and Line of Credit	2,304	2,300	4,568	4,561
Amortization of LP Units and Certain Other Awards	3,723	3,723	7,795	7,706
Special Charges	1,029	0	2,058	1,897
Intangible Asset and Other Amortization	2,157	2,157	4,314	4,314
Total Other Expenses	6,909	5,880	14,167	13,917
Investment Management [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	2,241	632	3,997	2,240
Acquisition and Transition Costs	0	0	108	21
Total Other Expenses	$ 0	$ 0	$ 108	$ 21